1. FIELD OF THE INVENTION
This invention pertains generally to variable resistors and more specifically to position sensors and switches cooperatively mated with pedal bracket structures.
2. DESCRIPTION OF THE RELATED ART
In the control of motors and machinery there are a number of interfaces that have been proposed through the years. These interfaces have sought to ease man's ability to perform the functions required in the operation of the machines with as little extraneous action and hardware as possible. In this way, an operator may perform as many functions as possible with minimal hinderance and with maximum control. That way, safety and efficiency are at a maximum.
One way of controlling a machine is with the use of pedals. These pedals allow input to the machine by use of an operator's foot, while simultaneously keeping hands free for other typically more complex tasks. These pedals are found in a variety of machines including pianos, sewing machines, and motive equipment such as automobiles and trucks.
The pedals used to control these devices in some cases are mechanical, typically incorporating a cable or various gears and other transmission devices to convert the limited rotary motion available from the pedal into useful mechanical motion to control the machine. Other pedals incorporate some type of position sensor that converts the mechanical position into an electrical signal. In the field of locomotion, particularly pertaining to automobiles and trucks, a mechanical bracket using a cable, often referred to as a Bowden cable, is the standard method for controlling the throttle of internal combustion engines. These pedal assemblies have a desirable feel and functionality and, with a few refinements, are extremely reliable. This type of pedal assembly defines many pedals today.
As noted above, through time there have been a number of attempts at different types of pedal devices to control machines. One major attempt has been to introduce an electrical linkage between the pedal and the device to be controlled. This is desirable since the gear assemblies are bulky, expensive and limited due to their inherent size to those applications where the pedal is very close to the controlled device. Mechanical linkages are not particularly flexible and are prone to sticking or binding. While the Bowden cable has proved generally reliable, the penetration of moisture and other contaminants may still cause the cable to bind. A cable less prone to failure is more expensive and bulky, and still inherently limited.
One early attempt at an electrical throttle controller is illustrated in U.S. Pat. No. 2,192,714. Therein, the throttle valve of an internal combustion engine could be controlled either by foot using a pedal or by hand using a knob. A second construction, illustrated for use with a forklift, is disclosed in U.S. Pat. No. 4,047,145. This second construction offers an ability to adjust the device for variances in manufacturing and performance among various assemblies.
More recently, there have been proposed devices that offer added safety features. This appeal is readily understood in view of the potential for harm of a several ton vehicle irreversibly set to full throttle. Even momentary loss of control, such as might occur with the false transmission of acceleration while in a line at a stoplight, may result in substantial damage. There has been sought a way to offer the desirable feel of the Bowden cable while improving reliability to ensure the safety of an operator and associated equipment. Heretofore, such a combination of features was not available for a price competitive with the Bowden cable.
In an effort to obtain the desired reliability, dual functions have been proposed in the prior art. The first of these is a pedal force switch or, performing a similar function, an idle validation switch. Exemplary patents illustrating such a combination are U.S. Pat. Nos. 5,133,225 and 4,869,220. However, each of these prior art patents forces movement of the position sensor to occur together with activation of the switch. Such a limitation does not allow for totally separate and independent functioning of the two devices and can lead to undetected failure modes. As noted, such undetected failure modes can cause much damage and may even lead to fatalities. The present invention seeks to overcome the limitation of the prior art.